When a user is attempting to use a service offered by a service company, the service company carries out authentication in order to determine whether or not the person trying to use the service is the authorized user.
The authentication methods currently being used include, for example, a method that uses a secret code, a method that uses a signature, a method that uses a seal, and a method that uses an ID code.
The method that uses a secret code is used, for example, for withdrawing cash from a bank account using a cash card. To withdraw cash, the user inserts a cash card into the card insertion opening of a bank ATM (automatic teller machine) and enters his/her secret code. The ATM sends both the card information (e.g., ID) read from the cash card and the secret code entered by the user to an authentication center. The authentication center carries out authentication based on the secret code entered into the ATM, the card information read, and a database that contains the correspondence relationship between the card information and secret code stored in a storage means.
The method that uses a signature is used, for example, for paying for merchandise using a credit card. To pay for merchandise using a credit card, the user enters his/her signature in a merchandise purchase slip. The merchandise seller carries out authentication by comparing the signature in the merchandise purchase slip with the signature on the credit card.
The method that uses a seal is used, for example, for withdrawing cash from a bank account using a passbook. To withdraw cash from a bank account using a passbook, the user places his/her seal on a cash withdrawal form. The bank carries out authentication by comparing the seal placed on the cash withdrawal form with the seal that has been pre-registered.
The method that uses an ID code is used, for example, for preventing unauthorized use of user equipment. In this method, the same ID code is stored in a tag (a card with send/receive functions, for example) worn by the user and in the user equipment (a mobile telephone, for example) that the user will use. Although the tag can be used connected to the user equipment, it is often used as a radio tag. The user equipment compares the ID code sent from the tag to the ID code it has in storage, and if the two ID codes match each other, the user equipment lock is released (a use-enabling signal is output, for example).
Another known authentication method is a method that uses biological information (voice pattern, fingerprint, retinal pattern, image of facial features, etc.) unique to each individual. This authentication method reads the user's biological information using a biological information reading device, and carries out authentication by comparing the biological information that has been read with the biological information that has been pre-registered. This authentication method is highly accurate since it uses biological information unique to each individual.
The conventional methods that carry out user authentication by means of a secret code, signature, seal, or ID code may incorrectly identify the person using the cash card, the person using the credit card, the person using the passbook, or the person carrying the tag in which the ID code is stored as the legitimate user even if he/she is not. For example, if the user equipment (e.g., cash card) or seal is stolen, or if the information, such as the secret code, signature, or ID code, is stolen or leaked, the user equipment could be illegally used.
On the other hand, the conventional methods that use biological information for user authentication result in higher overall system cost because they require a biological information reading device (e.g., an image-capturing device), a biological information processing device (e.g., an image-processing device and a large-capacity storage device), etc. Moreover, if a finger is injured or an eye disease is present, the fingerprint or retinal pattern may be altered, lowering the authentication accuracy. Additionally, if retinal patterns are used, it is necessary to bring the eyes to the measurement position, which can be cumbersome. If fingerprints are used, a finger must be placed directly on a fingerprint-reading device, which may cause psychological discomfort for people who are particularly concerned about cleanliness.